Discouraging news for Apple. NPD reckons that fewer people are buying its machines in the US as the credit crunch bites. Are we surprised? No. It was utterly predictable that, as the implausible high-wire act that was consumer spending in the US tipped over and began the long drop into recession, it would hit the companies that offered the highest-priced goods.

Houses aren't selling. The Humvee isn't selling. And BMW - a marque that people often compare to Apple, saying "Apple is like the BMW of computers - and you don't see them selling cheap ones!" - is pinning its hopes on the Mini, after seeing overall BMW sales drop by 24% year-on-year in January. (Soon after that piece appeared, it fired 850 agency staff at the Mini plant in Cowley. So perhaps things aren't even that good.)

So one question that Apple's executives might be considering on their regular Monday morning detail-fest, in which they go over what has sold and what hasn't, is: should Apple make a netbook?

Well, that's a good thing. If there's a single ray of light in the PC gloom, it's netbooks. Their sales are rocketing while larger models' are tanking. And there's another threat to Apple on the horizon: the upcoming Windows 7, which those who've tried it say is much more presentable and usable than Vista. If Microsoft can get Windows 7 out of the door in quick order, then the chance that Apple had to persuade people to switch from XP, or Vista, to Mac OSX will be gone.

The question is, would an Apple netbook chew up share from Windows, or would it cannibalise Apple's own sales?

There are two examples that Apple can follow from its own history: what it did with iPods, or what it did with the Mac mini.

First, iPods. There, it was a latecomer to an already-established (but nascent) market. It was expensive, and didn't sell that well - until Apple released the iPod mini in February 2004, two and a half years after the first iPod. And it was in Christmas 2004 that sales of iPods - all iPods together - suddenly rocketed. In 2005, Apple added the (lower-cost) iPod shuffle and, later that year, the iPod nano (effectively replacing the iPod mini). With that, it was all over the price range for digital audio players: bottom, middle, and top. It wasn't worried about cannibalising its own sales - in fact, it almost welcomed it as a way to make people upgrade from older versions to new ones.

By contrast, we have the Mac mini - Apple's grudging offering to the low-end market, introduced in January 2005 by Steve Jobs, who did it with a vague air of "Why the hell am I doing this again?" A "headless" machine - "bring your own keyboard, display and mouse" Jobs warned (shortened on the accompanying presentation slide to "BYOKDM") - the Mac mini was carefully designed not to cannibalise any of Apple's laptops or desktops. It was only worth buying, even when new, if you really did BYOKDM. And since then it has been allowed to fall further and further behind in processing power (as contributors to our letters pages have complained). Does the Mac mini threaten Apple's existing products? Not at all. But I doubt it's helping sales much either. These days, you can buy a netbook with almost as much processing power as a Mac mini for about a hundred pounds less. And it has a screen and keyboard.

The netbook plan looks like it would be a sensible one. Sure, Apple has enough money in the bank to ride out the recession. But if it loses its customer base, or its potential customer base (and note how sales of iPhones fell quarter-on-quarter in the last results), then it loses its future.

What sort of netbook should Apple make, then? The trend seems to be towards 10-inch screens; Asus has said it is going to stop making the 7-inch versions. People like bigger laptop keyboards too.

Apple sort of makes a netbook already - as in, something with reduced functionality: it's called the MacBook Air. Except that it presents it as a top-end product (and prices it accordingly), despite it having no CD or DVD player. Well, nor does my daughter's Eee PC from RM, and that weighs less than a MacBook Air to boot.

Apple needs to react to changing market conditions. It has before: when it last made a quarterly loss, in the first quarter of 2001, Steve Jobs realised it was because he had focussed on giving the computers DVD-reader drives, rather than CD-burning ones. A rapid focus on CD burners followed, along with heavier emphasis on iTunes: the CD-inspired "rip, mix, burn" is rather better than the DVD-gazing "insert, click, watch".

So should Apple introduce a netbook? Hell, yes. If it wants to get into a market that is expanding rapidly, which is giving an old version of Windows - the long-past-end-of-life XP, or "Windows Zombie" as it's becoming known to analysts - then it needs to roll its sleeves up. There's a big market there waiting to be tapped.

Will it cannibalise its own sales? Perhaps. But I'd bet that there are enough Apple fanatics out there who would buy a second Apple machine if it's a netbook, but simply can't extend their credit, or sense, to encompass an extra full-blown laptop.

Hell, even I might buy an Apple netbook. There seem to be enough people who have created their own "Hackintosh netbooks" that it must be feasible - perhaps even desirable.

So is Tim Cook brave enough to give this his go-ahead? It would certainly be a way to make his mark on the company. And if it proves to be a success - which I think it would - he could justifiably claim to have laid the foundations for becoming Apple's chief executive outright in the future. Remember, Tim, fortune favours the brave.